Precision assembly table and method

ABSTRACT

A precision assembly table and method includes a plurality of rigid bars connected to adjustable support members which can individually adjust the position of the rigid bars above a surface and a frame to create a desired contour. The structure to be assembled, such as a magnetic levitation guideway, is positioned and held in place on top of the rigid bars which have been positioned so as to define a desired contour of the structure and to which the structure will mechanically conform. The position of the rigid bars is monitored and adjusted by a computer to maintain the desired contour while the structure resting on the rigid bars is being assembled.

FIELD OF THE INVENTION

[0001] The present invention relates generally to an apparatus and amethod for precision manufacturing and assembly of contoured or curvedmetallic structures, and more particularly to the precisionmanufacturing and assembly of magnetic levitation vehicle guideways.

BACKGROUND OF THE INVENTION

[0002] The precision manufacture of contoured or curved metallicstructures such as guideways for magnetic levitation vehicles, bridgestructures such as highway overpasses, and offshore oil rig drillingplatforms is currently expensive, time consuming, and in many casesimpossible to perform within the tolerances mandated by the application.Magnetic levitation vehicle guideways, for example, are required to meetstringent tolerances in their manufacture in order for the magneticlevitation vehicles to properly and safely operate over the guideways.

[0003] Magnetic levitation vehicles are capable of traveling over three(3) eighty-two (82) foot long sections of guideway in one (1) second oftime, but can not operate over excess up, down, or side to sidenonconformities or departures from the design contour in the guideway.To accommodate such speeds and operation, an eighty-two (82) footsection of guideway must be manufactured and assembled so thatoperational components can be positioned to plus or minus 0.1 mm(one-tenth of one millimeter) tolerance of the design contour across thelength of the finished beam.

[0004] Current manufacturing and assembly methods are not capable of thetimely and cost-effective manufacture of contoured or curved metallicstructures, such as guide plates, bridge support beams, and oil rigsupports, to ensure that operational components can be positioned toplus or minus 0.1 mm (one-tenth of one millimeter) tolerance of thedesign contour across the length of the finished structures. Currentmethods of manufacture and assembly are labor intensive, imprecise, andexpensive. Such methods are unacceptable for the construction ofmagnetic levitation transportation systems.

[0005] For example, a recent proposed magnetic levitation transportationsystem required 650 guideway sections in 350 different configurations.Current labor intensive manufacturing methods for such a project arecost prohibitive.

[0006] In an age of budget cutbacks and cost-effective projects, a moreprecise, automated, inexpensive, and faster apparatus for and method ofmanufacture of precision structures is needed.

SUMMARY OF THE INVENTION

[0007] Disclosed is a precision assembly table comprising a frame, asurface connected to the top of said frame, and a plurality of rigidsupport bars above said surface that define a contoured surface uponwhich items to be assembled, such as magnetic levitation guidewaystructures, are positioned. The assembly table includes a plurality ofadjustable support members wherein each of said rigid support bars isconnected to at least two of said adjustable support members, andwherein said adjustable support members are connected to said frame,such that the position of each of said rigid support bars above saidframe and said surface is capable of individual adjustment and thecountered surface desired for the items being assembled, such as amagnetic levitation vehicle guideway, and defined by said rigid supportbars is capable of adjustment by adjustment of said adjustable supportmembers.

[0008] Further disclosed is a method of assembling a contouredstructure, such as a magnetic levitation vehicle guideway, comprisingpositioning of a portion of a structure on a manufacturing assemblytable comprising a plurality of individually adjustable bars that definea contoured surface, individually adjusting said plurality of adjustablebars to the desired contoured surface of said portion of a structure,holding the portion of the structure in position with a hold downfixture, allowing said portion of a structure to mechanically conform tosaid contoured surface established by said plurality of adjustable bars,and connecting the remaining portions of a contoured structure, such asa guideway, to the portion of the structure, such as a guide plate,positioned on the manufacturing assembly table after the portion of thestructure has conformed to said contoured surface to form said contouredstructure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a perspective view of the precision assembly table witha partial guideway assembly positioned on it.

[0010]FIG. 2 is a perspective view of the precision assembly table withits rigid bars positioned in a curved contour.

[0011]FIG. 3 is a cross-sectional view of one-half of the precisionassembly table depicting a screw mechanism as an adjustable supportmember connected to the rigid bar and table surface.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0012] The precision assembly table of the present invention consists ofa frame 1 connected to a surface 2 over which rigid bars 3 arepositioned by adjustable support members 4 which are connected to therigid bars 3 and the frame 1 and necessarily pass through the surface 2as depicted in FIGS. 1, 2 and 3. As depicted, the frame 1 supports thesurface 2 above the ground, and the frame further supports theadjustable support members 4 which protrude through the surface 2 tosupport the rigid bars 3 above the surface 2, above the frame 1, andabove the ground.

[0013] The frame 2 in the preferred embodiment is very rigid andconnected to the factory floor or ground to prevent movement of theframe 2, thereby avoiding interference with the assembly. The frame 2can be of a variety of configurations, provided that it provides a rigidand stable apparatus upon which the surface 2 and adjustable supportmembers 4 can be connected. The surface 2 is utilized to shield theframe 1 and the apparatus associated with the adjustable supportmembers, depicted in FIG. 3, from materials and damage resulting fromthe assembly operations taking place on top of the rigid bars 3.

[0014] The surface 2 as depicted in FIG. 3 may be used to supportapparatus associated with the adjustable support members but is notessential to the practice of the invention and operation of theprecision assembly table. The frame 1 may be used in connection with theadjustable support members 3 and rigid bars 2 without the presence ofthe surface 2, whereby the apparatus would perform the method ofassembly in the same manner. The structures to be assembled, such asguideways, are not required to, and preferably do not, rest on thesurface 2 but rather on the tops of the rigid bars 3 as depicted in FIG.1 which shows a magnetic levitation guideway guide plate 5 positioned onthe tops of the rigid bars 4.

[0015] In the preferred embodiments of using the precision assemblytable, a hold down fixture (not shown) for positioning and holding theitems being assembled in place on the top of the rigid bars 3 isutilized. The hold down fixture in the preferred embodiment preferablyconsists of a plurality of clamps holding the item to be assembled inplace on the top of the rigid bars 3, and for that purpose is preferablyconnected to the rigid bars 2 themselves or to the surface 2 or theframe 1, depending on, for example: (1) the application the precisionassembly table is being used for; and/or (2) any space restraintsimposed because of, for example, the building surrounding the precisionassembly table.

[0016] The rigid bars 3 in the preferred embodiment are made of lowthermal expansion coefficient metallic material such as INVAR orNi-span-C such that the heat of any welding performed on the items beingassembled on the rigid bars 3 minimally impacts the position and shapeof the rigid bars 3.

[0017] The assembly of items on the precision assembly table will mostpreferably be accomplished without the application of heat, other thanincidentally due to the effects of welding. Should the precisionassembly table or its components such as the rigid bars 3 and frame 1,and to a lesser degree the surface 2, become heated or elevated intemperature, cooling is preferably provided by the application of, forexample, a liquid coolant, most preferably water, on the surfaces of theprecision manufacturing table and its components. Alternatively, wateror another liquid coolant may be pumped through the frame 1, surface 2,and rigid bars 3 of the precision manufacturing table to keep suchcomponents at lower temperatures. Such cooling is intended, inter alia,to assist in the prevention of deformation due to heating and elevatedtemperatures. The use of coolants would especially be preferred if therigid bars were not made of a material with a low thermal expansioncoefficient.

[0018] The rigid bars 3 in the preferred embodiment for use in theassembly of magnetic levitation vehicle guideways would be parallel toeach other and approximately one foot apart. Other applications andparticularly complex or curved contours may require more rigid bars 3closer together. In some circumstances, the rigid bars 3 would notnecessarily need to be parallel to each other. Some applications wouldnot require as many rigid bars 3 such that the rigid bars 3 could beplaced more than one foot apart. The skilled artisan is credited withthe ability to ascertain any such requirements that such applicationsmay require with respect to such spacing.

[0019] The rigid bars 3 are supported above the surface 2 by adjustablesupport members 4. At least two adjustable support members 4 are mostpreferred to support and adequately position the rigid bars 3. Asdepicted in FIG. 1, a structure to be assembled, such as a guide waywith a guide plate 5, is most preferably positioned on the top surfaceof the rigid bars 3.

[0020] In a most preferred embodiment (as depicted in FIG. 3), theadjustable support members 4 comprise a screw 14 connected to the rigidbar 3 by a ball 9 and socket 8 on one end and to a precision worm gear11 connected to an electric servo motor 12 on the other end. The socket8 on the opposite end of the rigid bar 3 (not shown) in a preferredembodiment would be affixed in a slot (not shown) within the rigid bar 3or affixed to the rigid bar 3 to allow the length of the span of therigid bar 3 between the two sockets 8 to vary so as to accommodateadjustment of the position of the rigid bar 3. The screw 14 protrudesthrough an opening in the surface 2 and is held in place by a fixedthreaded collar 10 connected to the surface 2 and the frame 1 of theprecision assembly table.

[0021] In a particularly preferred embodiment, the screw 14 pitch yieldsa 5.0 mm (five millimeters) or less elevation change per a 360 degreerotation. The precision worm gear 11 preferably has a reduction ratio of100:1 or greater. The electric servo motor 12 is preferably controlledto plus or minus 15 degrees in rotation, most preferably by computerinput. Thus, by way of example, for a one degree rotation of theelectric servo motor 12, the adjustment in the height of the rigid bar 3above the surface 2 would be 0.013 mm. As a further example, for a onetwenty-fourth of one degree rotation, the adjustment would be 0.000579mm. Many other screw 12 pitch, precision worm gear 11 reduction ratios,and electric servo motor 12 rotations are, therefore, possible as theforegoing indicates.

[0022] In the most preferred embodiment, the rigid bars 3 are square orslightly rectangular shaped in cross-section. The top surface of therigid bars 3 are shaped as elongated rectangles as are the sides andbottom of the rigid bards 3. Other shapes for the rigid bars 3 arepossible and contemplated, provided that a surface is provided on whichthe items to be assembled can be positioned.

[0023] Preferably, an item such as the guide plate 5 of a magneticlevitation vehicle guideway depicted in FIG. 1 is positioned on andrests on the plurality of rigid bars 3. The guide plate 5 or otherstructure positioned on the rigid bars 3 is held in position by a holddown fixture, such as a clamps, at various locations on the guide plate5 or other structure. The rigid bars as depicted in FIG. 1 can bepositioned relatively flat or parallel to the surface 2. In such a caseand other similar situations, a hold down fixture would not benecessary.

[0024] The rigid bars 3 can be individually adjusted to positions ofvarying height above the surface 2, as depicted in FIG. 2. For example,one end of each rigid bar 3 can be positioned at a different height thanthe other end of that same rigid bar 3 to form complex contours withcomplex curves, as depicted in FIG. 2. The adjustable support members 4are preferably extended to varying heights above the surface 2 toposition the rigid bars 3 at varying heights above the surface. Holddown fixtures such as clamps would preferably be used to hold thestructure, such as the guide plate 5 depicted in FIG. 1, to the rigidbars 3 which are positioned in complex shapes as depicted in FIG. 2.

[0025] The tops of the rigid bars 3 depicted in FIG. 2 preferably form acomplex shape to which the structure, such as a guide plate 5, conformsto mechanically, by either the application of a hold down fixture topress or hold the structure (such as a guide plate 5) in contact withthe tops of the rigid bars 3 or by the force of gravity. For thinstructures, such as guide plates, or for relatively flat contours, asdepicted in FIG. 1, gravity will suffice to mechanically shape thestructure to the contour defined by the tops of the rigid bars 3. Forthicker structures or complex contours, as depicted in FIG. 2, a holddown fixture is most preferably utilized to mechanically shape thestructure to the contour defined by the tops of the rigid bars 3. Oncethe structure, such as the guide plate 5 depicted in FIG. 1, hasconformed to the desired contour due to gravity or the application of ahold down fixture, the various other pieces of the structure, such asthe guide way structure 6, 7 depicted in FIG. 1, can then be welded orattached to contoured portion of the structure on the precision assemblytable, such as the guide plate 5 as depicted in FIG. 1.

[0026] In order to ensure maximum precision and speed, the height andposition of the rigid bars 3 and adjustable support members 4 arepreferably calculated by and controlled by a computer. The initialposition of the rigid bars 3 is preferably determined and the positionsof the adjustable support members 4 and the rigid bars 3 connectedthereto are then positioned. To accomplish the positioning, a computeris preferably linked directly into the controls for the adjustablesupport members 12, or the electric servo motors 12 used to position theadjustable support members 4 as depicted in FIG. 3.

[0027] In a preferred embodiment, while the various pieces of thestructure are being assembled on the precision assembly table, the forceand heat of the welding and attachment being performed may change theposition of the rigid bars 3, such that the desired contour formed bythe tops of the rigid bars 3 is not held. To ensure that the desiredcontour is held, sensors, or a reflector 13 as depicted in FIG. 3, arepreferably connected to both ends of a rigid bar 3. Sensors orreflectors 13 are preferably attached to both ends of every rigid bar 3to ensure maximum measurement. Alternatively, sensors or reflectors 13can be attached to every other rigid bar 3 or some lesser or greaterfraction thereof.

[0028] In a preferred embodiment, a laser scan is used to scanreflectors 3 attached to the ends of each rigid bar 3 and to determinethe positions of the rigid bars 3. The results of the laser scanmeasurements are then input into a computer which compares the scannedpositions of the rigid bars 3 with the desired positions of the rigidbars 3. The computer can then determine the amount of adjustment neededfor the adjustable support members 4 to move the rigid bars 3 to theirdesired or design positions. The computer can then send signals via itsdirect link to the controls or electric servo motor 12 of eachadjustable support member 4 to make any adjustments. This feedback typeof measurement and adjustment can be repeated as often as necessary,preferably continuously, while the structure is being assembled on theprecision assembly table. The computer and laser scan or othermeasurement device or sensors can also be used to initially set thepositions of the rigid bars 3.

[0029] Preferably, the structure to be assembled can be placed on theprecision manufacturing table before the rigid support bars 3 arepositioned in the desired configuration. More preferably, the rigid bars3 would be positioned in the desired contour prior to the placement ofthe structure on the rigid bars 3 to prevent the loading of theadjustable support members due to the weight of the structure on therigid bars.

[0030] The embodiments described above are to be considered in allrespects only as illustrative and not restrictive. The scope of theinvention is indicated by the following claims rather than the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. A precision assembly apparatus comprising: a frame; a plurality of rigid bars upon which items to be assembled are positioned; and means for connecting said rigid bars to said frame and adjusting the position of said bars relative to said frame such that the plurality of said bars defines a desired contour that said items to be assembled will be positioned upon and to which said items to be assembled will mechanically adjust.
 2. A precision assembly apparatus comprising: a frame; a plurality of rigid bars upon which items to be assembled are positioned; a plurality of adjustable support members wherein each of said rigid bars is connected to at least two of said adjustable support members and wherein said adjustable support members are connected to said frame such that the position of each of said rigid bars above said frame is capable of individual adjustment and the contour defined by such rigid bars is adjustable by adjustment of said adjustable support members; and a hold down fixture capable of holding said items to be assembled in position.
 3. The precision assembly apparatus in claim 2 wherein each of said adjustable support members is a screw.
 4. A precision assembly table comprising: a frame; a surface connected to the top of said frame; a plurality of rigid bars above said surface that define a contoured surface upon which items to be assembled are positioned; a plurality of adjustable support members wherein each of said rigid bars is connected to at least two of said adjustable support members and wherein said adjustable support members are connected to said frame such that the position of each of said rigid bars above said frame and said surface is capable of individual adjustment and the countered surface defined by said rigid bars is capable of adjustment by adjustment of said adjustable support members; and a hold down fixture capable of holding said items to be assembled in position.
 5. The precision assembly table in claim 4 wherein each of said adjustable support members comprises a screw.
 6. The precision assembly table in claim 4 wherein each of said adjustable support members comprises a screw connected to said rigid bar with a ball and socket and wherein said screw is adjusted by operation of an electric servo motor upon a worm gear connected to said screw.
 7. The precision assembly table in claim 4 further comprising: position sensors connected to the ends of said rigid bars capable of monitoring the position of said rigid bars.
 8. The precision assembly table in claim 4 further comprising: reflectors connected to the ends of said rigid bars capable of measuring the position of said rigid bars by application of a laser scan on said reflectors.
 9. The precision assembly table of claim 4 wherein said rigid bars are positioned parallel to each other.
 10. The precision assembly table of claim 4 wherein the adjustment of the adjustable support members and position of said rigid bars is computer controlled.
 11. A precision magnetic levitation vehicle guideway assembly table comprising: a frame; a surface connected to the top of said frame; a plurality of rigid bars above said surface that define a contoured surface upon which the guide plate of a magnetic levitation vehicle guideway to be assembled is positioned; a plurality of adjustable support members wherein each of said support bars is connected to at least two of said adjustable support members and wherein said adjustable support members are connected to said frame such that the position of each of said rigid bars above said frame and said surface is capable of individual adjustment and the countered surface defined by said rigid bars and to which said guide plate will mechanically conform is capable of adjustment by adjustment of said adjustable support members; and a hold down fixture capable of holding said guide plate in position.
 12. The precision assembly table in claim 11 wherein each of said adjustable support members comprises a screw.
 13. The precision assembly table in claim 11 wherein each of said adjustable support members comprises a screw connected to said rigid bar with a ball and socket and wherein said screw is adjusted by operation of an electric servo motor upon a worm gear connected to said screw.
 14. The precision assembly table in claim 11 further comprising: position sensors connected to the ends of said rigid bars capable of monitoring the position of said rigid bars.
 15. The precision assembly table in claim 11 further comprising: reflectors connected to the ends of said rigid bars capable of measuring the position of said rigid bars by application of a laser scan on said reflectors.
 16. The precision assembly table of claim 11 wherein said rigid bars are positioned parallel to each other.
 17. The precision assembly table of claim 11 wherein the adjustment of the adjustable support members and position of said rigid bars is computer controlled.
 18. A method of assembling a contoured structure comprising: individually adjusting a plurality of rigid bars to the desired contoured surface of a portion of said contoured structure on a precision assembly table comprising said plurality of rigid bars whose position is capable of individual adjustment and that define a contoured surface; positioning said portion of said contoured structure on said plurality of rigid bars; holding said portion of said contoured structure in position on said plurality of rigid bars disposed to form the desired contour with a hold down fixture; allowing said portion of said contoured structure to mechanically conform to said contoured surface established by said plurality of rigid bars; and connecting the remaining portions of said contoured structure to said portion of said contoured structure positioned on said precision assembly table after said portion of said contoured structure has conformed to said contoured surface to form said contoured structure; measuring the position of said rigid bars during assembly operations; and adjusting the position of said rigid bars so that their position conforms to the desired contour.
 19. A method of assembling a guideway for a magnetic levitation vehicle comprising: individually adjusting a plurality of rigid bars to the desired contoured surface of a guide plate for said guideway on a precision assembly table comprising a plurality of rigid bars whose position is individually adjustable and that define a contoured surface; positioning of said guide plate of said guideway on said plurality of rigid bars; holding said guide plate of said guideway in position on said plurality of rigid bars disposed to form the desired contour with a hold down fixture; allowing the surface of said guide plate to mechanically conform to said contoured surface established by said plurality of rigid bars; welding stiffeners and support plates to said guide plate after it has conformed to said contoured surface to form a guideway; measuring the position of said rigid bars during assembly operations; and adjusting the position of said rigid bars so that their position conforms to the desired contour. 